{eval}
   {eval} is used to evaluate a variable as a template. This can be used
   for things like embedding template tags/variables into variables or
   tags/variables into config file variables.
  
   If you supply the special "assign" attribute, the output of the
   {eval} function will be assigned to this template variable instead of
   being output to the template.
 
Technical Note: 
   Evaluated variables are treated the same as templates. They follow
   the same escapement and security features just as if they were
   templates.
  
Technical Note: 
   Evaluated variables are compiled on every invocation, the compiled
   versions are not saved! However if you have
   caching
   enabled, the
   output will be cached with the rest of the template.
  
| Example 8-5. {eval} | setup.conf
   ----------
   emphstart = <strong>
   emphend = </strong>
   title = Welcome to {$company}'s home page!
   ErrorCity = You must supply a {#emphstart#}city{#emphend#}.
   ErrorState = You must supply a {#emphstart#}state{#emphend#}. | 
 
   Where index.tpl is:
   | {config_load file="setup.conf"}
   {eval var=$foo}
   {eval var=#title#}
   {eval var=#ErrorCity#}
   {eval var=#ErrorState# assign="state_error"}
   {$state_error} | 
 
   The above example will output:
   | This is the contents of foo.
   Welcome to Foobar Pub & Grill's home page!
   You must supply a <strong>city</strong>.
   You must supply a <strong>state</strong>. | 
 |